As semiconductor device features continue to shrink in size, the task of meeting photoresist performance requirements for high resolution, low line edge roughness (LER) and high photo speed grows increasingly difficult. The challenges in simultaneously meeting the requirements for resolution, LER, and sensitivity are known in the art as the “RLS Tradeoff.” Current generation chemically amplified photoresists, designed to be developed in alkaline base, are capable of high photo speeds, but exhibit unsatisfactory resolution and LER as feature sizes approach 20 nm. In comparison, high-performance solvent-developed non-chemically amplified resists, such as PMMA (poly methyl methacrylate) resists, have excellent resolution and LER, but have unacceptably poor photospeed in optical imaging.
The use of solvent development in lithography is not a new idea. In the 1950s, the earliest photoresist systems used organic solvents for developing resist films. See, e.g., William S. DeForest, Photoresist: Materials and Processes, McGraw-Hill, New York, 1975. The first generation 248 nm chemically amplified resist, the TBOC (t-butyloxycarbonyloxy) styrene resist, was described 25 years ago for development in an organic solvent. See, e.g., Ito et al., SPIE 0771, 24 (1987); and Maltabes et al., SPIE 1262, 2 (1990). Since the development of the TBOC resist, virtually all chemically amplified resists have been designed to be developed in aqueous base solutions; consequently, development of solvent-based resists has been largely ignored as an option for modern high resolution chemically amplified resists. Today, there is an on-going interest in organic developers for negative tone chemically amplified resists (see, e.g., U.S. Pat. No. 7,851,140 B2 to Tsubaki); however, there are few examples of organic developers for positive tone chemically amplified resists. The present invention addresses this need in the art.